GB2023853A

GB2023853A - Apparatus for checking parallelism of vehicle wheels

Info

Publication number: GB2023853A
Application number: GB7921525A
Authority: GB
Original assignee: M ETS; Muller et Cie SA
Current assignee: M ETS; Muller et Cie SA
Priority date: 1978-06-23
Filing date: 1979-06-20
Publication date: 1980-01-03
Also published as: DK248479A; ES481487A1; FR2429413B1; FR2429413A1; GB2023853B; DK156850B; DK156850C; IT7949518A0; IT1162646B; DE2924743A1; DE2924743C2

Abstract

Apparatus for checking the parallelism of the front or rear wheels 2a,2b of a vehicle, comprises two arms 1a,1b intended to be fixed horizontally against the external faces of the two wheels to be checked and means for ascertaining the parallelism of these wheels. At the extremity 5 of each horizontal arm opposite to that intended to be fixed against a wheel, there is provided a pivoting element 6a, 6b adapted to project or reflect a light beam in the direction of the corresponding extremity of the other arm, and a checking sighting mark intended to receive the light spot coming from the projection or reflection element provided on the other arm of this apparatus. The rotation of each projection or reflection element is controlled by a graduated drum 14 the scale zero of which is opposite to a fixed index when the light beam coming from the reflection element is oriented at right angles to the corresponding arm of this equipment. <IMAGE>

Description

SPECIFICATION Apparatus for checking parallelism of vehicle wheels The present invention relates to apparatus utilised for checking the parallelism of the front or rear wheels of a vehicle.

More precisely it concerns apparatus of the kind comprising two arms intended to be fixed horizon tallyagainstthe outerfaces ofthetwo wheels to be checked which themselves comprise means for checking their parallelism. In certain apparatus of this kind the provided checking means consist of a light projector disposed at the free extremity of each horizontal arm and adapted to project a light spot on to an inspection scale provided at the corresponding extremity of the other arm. These two light projectors are fixed in such manner that each of them directs a light beam at right angles in relation to the axis of the corresponding arm.Under these circumstances, when the two wheels being checked are parallel, the light spot emitted by each projector is situated on the zero of the scale of the corresponding extremity of the other arm. If this is not the case, the operator can deduce that the two wheels are not parallel, and he can then observe the magnitude of the defect of parallelism and its direction (toe-in or toe-out), according to the position of the spot projected by each projector on to the scale of the opposite arm.

However this checking method is not very practical, especially since the value of the angle of toe-in or toe-out is not read directly.

This is why the present invention has for object an apparatus of the same type, which however is designed in such manner as to simplify the checking operations while avoiding all risk of error.

This apparatus is essentially characterised in that, at its extremity opposite to that intended to be fixed against a wheel, each horizontal arm comprises: firstly, a pivoting element adapted to project or reflect a light beam in the direction of the corresponding extremity of the other arm; next, a checking sighting mark intended to receive the light spot coming from the projection or reflection element provided on the other arm of this apparatus; the rotation of each projection or reflection element being controlled by a graduated drum the scale zero of which is opposite to a fixed index mark when the light beam coming from this element is oriented at right angles to the corresponding arm of the apparatus.

Therefore, when the two control drums are disposed in this position, the light spot received by each checking sighting mark must be situated on the fixed reference mark of the latter if the two wheels are parallel. If this is not the case the operator can deduce therefrom that there is a toe-in or toe-out between the two wheels to be checked. Then the control drum provided on each horizontal arm should be rotated until the moment when the corresponding light spot is then projected on to the reference mark of the opposite sighting mark. It is sufficient to read off the value from the scale of each drum situated opposite to the fixed corresponding reference mark, to know the value of the angle of toe-out or toe-in between the two wheels.

Thus the present apparatus affords easy and speedy checking of the parallelism of the two wheels.

However further particular features and advantages of this apparatus will appear in the course of the following description of an example of embodiment thereof. This description is given simply by way of indication with reference to the accompanying drawing, wherein: Figure 1 is a diagrammatic perspective view illustrating the manner of utilisation of the present apparatus, Figure 2 is a view in elevation representing the two wheels of a vehicle in the course of checking, independently of the actual structure of the vehicle, Figure 3 is a corresponding plan view, Figure 4 is a perspective view illustrating the manner of fitting of one of the checking arms of the present apparatus on a vehicle wheel, Figure 5 is a partial perspective view of such a checking arm, represented on a different scale, Figure 6 is a partial sectional view along the line VI - VI in Figure 5, but on a different scale, Figure 7 is a diagrammatic perspective view of the device provided on each checking arm.

As already indicated, the present apparatus comprises two checking arms la and lb intended to be fixed horizontally against the outer faces of the two wheels 2a and 2b of an axle to be checked, for example the front axle in the case as illustrated in Figure 1. At one of its extremities each of these arms is fast with the lower extremity of a support 3 capable of being fixed against the outer face of the rim flange of a wheel by means of appropriate attachment elements, for example arms 4 capable of being applied against the rim flange or of being hooked over it.

The two arms lea and ib are fixed so that they extend horizontally towards the corresponding extremity of the vehicle, in the present case the foward extremity when the purpose is to check the two wheels of the front axle. In this connection it should be noted that the extremities 5 of these two arms which are opposite to their support 3 are thus situated forward of the two checked wheels and at a level lower than that of the body of the vehicle.

At its free extremity 5 each checking arm la or lb comprises a mirror, 6a or 6b respectively, mounted for pivoting about a vertical axis. In its rest position this mirror is oriented at 45" in relation to the axis of the corresponding checking arm, so as to direct towards the similar extremity of the opposite arm a light beam coming from a light projector 7 situated to the rear on the same arm as the mirror under consideration.

The two checking arms can be constituted by metallic sections, for example tubes of square or rectangular section, as is the case in the example as represented. In such a case the light projector 7 carried by each arm and the corresponding mirror 6a or 6b are both housed within this tube, which has the advantage that their protection against impacts is ensured. Then a window 8 is formed in the corresponding face of the free extremity of each checking arm to permit the emergence of the light beam reflected by the corresponding mirror 6a or 6b.

Each of these mirrors is carried by a vertical rotating shaft 9 on which there is fixed one of the extremities of a control crank 10 disposed outside the corresponding checking arm but enclosed within a protective casing 11. The opposite extremity of this crank is disposed between a spring 12 and a thrust screw 13fastwith a control drum 14. Thus by rotating this drum in one direction or the other it is possible to pivot the corresponding mirror 6a or 6b either in the direction of the arrow F1 or contrarily in the direction of the arrow F2.

The drum 14 comprises a scale moving in front of a fixed index mark. The arrangement is such that when the zero of this scale is disposed opposite to this index mark, the corresponding mirror 6a or 6b is oriented very precisely at 45" in relation to the axis of the respective checking arm so that the beam reflected to the exterior by this mirror is oriented at 900C in relation to this arm.

A second drum 15 is associated with each control drum 14. However this drum is mounted freely instead of being coupled by the thrust screw 13, as is the case for each drum 14. The rôle of this second drum will appear in the course of the subsequent description of a manner of utlisation of the present equipment.

Of couse each protective casing 11 comprises a window 16 opposite to the window 8 provided on the free extremity of the corresponding arm 1a or 1 b.

However above this window each casing comprises an aperture situated opposite to a checking sighting mark 17 fast with the corresponding arm, this sighting mark possibly possessing a simple vertical reference line. However for preference one or more vertical reference lines are provided on either side of this central reference mark.

To carry out the checking of the parallelism of the two wheels of an axle by means of the present equipment the following procedure is adopted: After the two checking arms la and 1b have been fixed as represented in Figure 1, it being ensured that they are horizontal, the control drum 14 of the checking device of each of these arms is placed in its position in which the zero of its scale is situated opposite to the reference index. If the light spot reflected by each mirror 6a or 6b is situated on the central reference mark of the sighting mark of the opposite arm, this signifies that the two wheels checked are perfectly parallel with one another.In this connection it should be noted that the precision of the check carried out results from the fact that a vertical line is disposed in front of each light projector 7, so that it is the image of this line which must come into superimposition on the central reference mark of the sighting mark provided on the opposite checking arm.

If this is not so, the operator must rotate the control drum 14 of the checking device of one of the arms until the moment when the light beam coming from this arm strikes upon the central reference mark of the sighting mark of the opposite arm. When this result is achieved, the operator reads the scale carried by this drum, which is now situated opposite to the fixed reference mark.

He then carries out the same operation upon the other checking arm and makes the algebraic addition of the two values thus obtained. In fact the scales provided on the two drums 14 are established in such manner as directly to indicate the value of the toe-in or toe-out angle formed between the two checking arms and consequently between the two wheels.

In order to eliminate the algebraic calculation of the two values read from the control drums 14 it is possible to use the two free drums 15 associated with these. However these two free drums also have the function of permitting of reading the variations of parallelism, wheel by wheel, as a function of the height of the rack existing on the suspensions of certain particular types of vehicles. In fact, in certain vehicles, a variation of the height of this rack can involve variations of parallelism of the wheels. Now these variations must remain within a certain tolerance limit, and this should be ensured in the checking of the vehicle.

To this end the suspension is artifically constrained into a low position by compression, and the light rays coming from each arm are brought on to the fixed reference mark of the opposite sighting mark by rotation of the control drums 14 in one direction or the other. When this is realised, the zero of each free drum associated with a control drum is placed opposite to the same fixed index. Then, when the suspension has been allowed to resume its high position, the two control drums are rotated afresh so as to obtain coincidence of the light rays with the central reference marks of the two checking sighting marks. On reading of the scale of each free drum 15 situated opposite to the corresponding fixed index, the difference of orientation of each wheel between the two corresponding positions of the suspension is known.Thus it is possible to check whether the situation remains within the tolerance foreseen by the designer. If this is not so, it is possible to remedy the detected fault by operating in accordance with the designer's instructions. However it is then possible to check afresh that this defect has been eliminated, by means of the present equipment.

In this connection it should be noted that the equipment permits likewise of monitoring the operations of elimination of any defect in parallelism. In fact, by maintaining the present equipment in action during the adjustment of the parallelism of the two wheels, the operator can immediately be aware of the moment when he has obtained the correction of the defect of parallelism.

However, as already indicated, the principal advantage of the present equipment over those already known consists in the simplicity of the present equipment and in the fact that the operator can directly read the value of the toe-out or toe-in angle in the case of a defect of parallelism, without any risk of error.

However it is self-evident that the present equipment can be the object of numerous modifications and different forms of embodiment. Thus instead of comprising a fixed projector associated with a pivoting mirror, each checking arm could simply carry a pivoting projector disposed in the position of the orientable mirror 6a or 6b. In effect the same result would be obtained then as with the abovedescribed equipment. Moreover it would be possible to exploit differently the information likely to be supplied by operation of the control drums 14. The latter could in fact be associated with potentiometers connected into electric circuits comprising indicator apparatuses permitting knowledge of the amplitude of the variations of position of the control drums. In such a case of course the scales provided in these measurement apparatuses would be established in such manner as directly to indicate the value of the toe-in or toe-out angle between the two horizontal checking arms.

Finally it is self-evident that the checking arms can be associated with other measurement or checking apparatuses intended to be fixed against the two wheels of one of the axles of a vehicle, for example apparatus intended to check the other principal angles of the geometry of the front suspension of a vehicle.

Claims

1. Apparatus for checking the parallelism of the front or rear wheels of a vehicle, comprising two arms intended to be fixed horizontally against the external faces of the two wheels to be checked and comprising means permitting of ascertaining the parallelism of these wheels, wherein at its extremity opposite to that intended to be fixed against a wheel, each horizontal arm comprises firstly a pivoting element adapted to project or reflect a light beam in the direction of the corresponding extremity of the other arm, and a checking sighting mark intended to receive the light spot coming from the projection of reflection element provided on the other arm, the rotation of each projection or reflection element being controlled by a graduated drum the scale zero of which is opposite to a fixed index when the light beam coming from the reflection element is oriented at right angles to the corresponding arm of this equipment.

2. Checking apparatus as claimed in claim 1, wherein the pivoting element provided on the extremity of each checking arm is a mirror associated with a light projector disposed on the same arm close to its opposite extremity.

3. Checking apparatus as claimed in claim 2, wherein each checking arm is constituted by a tube within which the corresponding pivoting mirror and the light projector associated with this mirror are disposed, a window being formed on the internal face of each arm opposite to the pivoting mirror thereof.

4. Checking apparatus as claimed in any one of the preceding claims, wherein the pivoting projection or reflection element for a light beam is carried buy a rotating vertical shaft fast with a drive crank the opposite extremity of which is actuated by a screw fast with the corresponding control drum.

5. Checking apparatus as claimed in claim 4, wherein a free drum is associated with the control drum provided on each checking arm, this free drum being provided with a scale similar to that of the control drum.

6. Checking apparatus as claimed in any one of the preceding claims, wherein instead of comprising a scale each rotary control drum is associated with means for monitoring its angular position, for example a potentiometer connected into an electric circuit comprising an indicator apparatus sensitive to the variations of the characteristics of the current, caused by this potentiometer, which indicatorappar- atus can be graduated so as to indicate directly the value of the toe-in or toe-out angle between the two checking arms.

7. Checking apparatus substantially as described with reference to the accompanying drawings.